A five-truck convoy organised by the ICRC, the United Nations and the Syrian Arab Red Crescent had been due to deliver baby milk and medical and school supplies. "Beyond allowing this initial convoy through, the ICRC and its partners need concerned authorities to let it provide other essentials such as food," said the ICRC.

A UN spokesman said it had decided not to go ahead with the convoy after "nutrition items" were removed from the convoy.

One civilian died in regime shelling in Daraya on Thursday afternoon, said the Syrian Observatory for Human Rights.

In the northern city of Aleppo, emergency workers reported no deaths in eastern rebel-held areas since the local truce expired on Wednesday night. But two civilians including a woman died in sniper fire on the divided city's regime-controlled west, said the Observatory.

That truce came after a spike in violence that killed more than 300 civilians on both sides of the city last month.

The meeting next Tuesday between world powers in Austria comes as jihadists have dealt a series of setbacks to President Bashar al-Assad's troops in the country's centre.

In Hama province, Syria's Al-Qaeda affiliate - Al-Nusra Front - and its allies Thursday captured Zara village, where most residents hail from the same offshoot of Shiite Islam as the president, the Observatory said.

In nearby Homs, also central Syria, fighting has raged near the Shaer gas field - one of the biggest in the province - after the Islamic State group seized it from the regime last week.

Talks have also faltered over the fate of Assad, with the opposition insisting any peace deal must include his departure. But Damascus says his future is non-negotiable.

The head of Syria's main opposition group taking part in negotiations has told AFP forces fighting the regime need "actions, not words" from countries that support them.

"What we want are practical and effective measures on the ground. We don't need statements or pretty words in the media because that doesn't produce any results," said Riad Hijab. He called for tougher action against Assad, who he claimed had effectively received a "green light" from Moscow and Washington to continue bombing civilian areas.

Millions have fled Syria's conflict since it started with anti-government protests in 2011.

These include 20 percent of Syria's Palestinian refugees, the head of the UN Palestinian refugee agency said Thursday. Before the war, Syria was home to about 560,000 Palestinians whose ancestors fled the 1948 foundation of Israel and ensuing conflicts.